Conventional peanut butters consist of a mixture of solid nut particles, liquid oil, and in general, sugar and salt. The peanut butter is made by roasting and blanching raw peanut kernels and then grinding them. The comminuted nut particles are suspended in the oil to form a product having a pasty and spreadable consistency. In time, however, the oil will separate from the product and form a separate layer on the top and a rigid crumbly mass underneath. This tendency of peanut butter to separate on standing can be overcome to some extent by the use of suitable stabilizers such as by incorporating in the peanut butter partially hydrogenated or highly hydrogenated fats and oils.
It is known that the addition of these hydrogenated fats and oils stabilize the peanut butter by forming a crystal matrix which lends rigidity to the mass and prevents settling of peanut particles. However, to obtain the desired texture at high temperatures (80.degree.-100.degree. F.) these additives generally have high melting points (between 110.degree. F. and 150.degree. F.). When these high melting materials are added to the peanut butter in a quantity large enough to stabilize the oil, the peanut butter becomes excessively firm at the ordinary temperatures of use. As a result, the product is difficult to spread, has a waxy taste, slow mouthmelt, and tends to cling to the roof of the mouth when it is eaten.
The delicate balance required to prevent oil separation without sacrificing too much low temperature spreadability and without incurring a waxy mouth impression is difficult to obtain.
Another disadvantage of the use of the hydrogenated fat stabilizer is the wide variance of product quality which results from the variations in temperature during processing. In grinding peanuts to make peanut butter the temperature of the product increases to about 160.degree. F. or higher. The stabilizing material is added during the grinding step or while the product is at an elevated temperature. In common commercial practice the product is then rapidly chilled, customarily using a device such as a scraped wall heat exchanger to a temperature below the freezing point of at least a portion of the fat solids present in the product. The heat exchanger outlet temperatures may range from as low as 70.degree. F. to as high as about 120.degree. F. Variations in this outlet temperature frequently occur during the manufacturing, and may vary substantially within a day.
Wide variations in product quality can also be caused by variations in mechanical agitation of the partially formed crystal matrix during chilling. Any physical working of peanut butter stabilized by hydrogenated fat after it is chilled but, prior to the time it is packaged, will influence greatly the firmness and degree of stabilization of the peanut butter.
The manufacturing variance problems are minimized by the use of a stabilizer consisting of hydrogenated rapeseed oil having an iodine value not greater than 10. See U.S. Pat. No. 3,129,102 issued to Sanders (1964). U.S. Pat. No. 3,265,507 issued to Japikse (1966) discloses a peanut butter stabilizer which provides improved flavor. This stabilizer is a mixture of a beta phase tending hardstock and a non-beta phase tending hardstock. The preferred mixture is a mixture of hydrogenated soybean oil and hydrogenated rapeseed oil. However, because the melting points of these additives are high, the resulting peanut butter does not give a rapid mouthmelt, and tends to be stiffer at the lower use temperatures, in the region of 50.degree. F.
An object of the present invention is to produce a peanut butter which has good mouthmelt properties and reduced stickiness.
Another object of this invention is to provide a peanut butter of improved texture, i.e. less stiff and waxy without sacrificing stability.